Motor-driven syringe



Dec. 27, 1960 D. F. HYDE 2,966,175

MOTOR-DRIVEN SYRINGE Filed July 14, 1958 2 Sheets-Sheet 1 5o Inventor Dav id. f

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fi-Horneg 5 United States Patent MOTOR-DRIVEN SYRINGE David F. Hyde, Chicago, Ill., assignor to Central Scientific Company, Chicago, Ill., a corporation of Illinois Filed July 14, 1958, Ser. No. 748,233

15 Claims. (Cl. 141-27) This invention relates to a motor-driven syringe for use in the accurate volumetric delivery of liquids and finds important application in titrations wherein unknown solutions are identified by accurately measuring the amount of liquid reagent that must be added to bring the unknown solution to a predetermined end point. More particularly, this invention is concerned with a motordriven syringe wherein the volume of liquid delivered thereby is automatically controlled, measured and indicated in the form of a digital presentation.

In the past, reagent delivery in titrations has been carried out in a number of ways. Originally, handoperated syringes and burets were employed. With the advent of automatic control for titrations, however, these manual devices became outmoded. Electrically controlled solenoid-operated burets were then used, but they have been found to be inaccurate and difficult to read. Even hand-operated syringes are more serviceable than automatically controlled burets. More recently, coulometn'c supply of reagent by electrolysis in situ has been promoted, but this technique is of limited versatility and may frequently require special mounting arrangements for the electrodes, depending on the type of end point detection equipment that is employed. Thus, there exists a real need for volumetric reagent delivery equipment that complements and derives full benefit from the advances which have been made in the associated end point detection and control equipment.

The principal object of the invention is to provide a highly accurate, reliable and versatile motor-driven syringe arrangement that will satisfy this need.

Other objects and advantages will become apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same;

Fig. 1 is a diminutive perspective view of the motordriven syringe unit of this invention in association with an automatic titration end point detector unit that includes means for automatically cutting off the supply of reagent from the syringe unit;

Fig. 2 is a detailed vertical sectional view through the motor-driven syringe unit of Fig. 1, with the syringe and portions of the outer casing omitted;

Fig. 3 is a fragmentary side-sectional view of the syringe-mounting arrangement;

Fig. 4 is a plan view of the driving-gear arrangement at the base of the apparatus and is taken along the line 44 of Fig. 2; and

Fig. 5 is a diagrammatic illustration of the control circuit for the motor-driven syringe unit.

Referring now to the drawings and particularly to Fig. l, the motor-driven syringe unit of this invention, as indicated at 10, is shown in operative association with a titration unit 11 that includes facilities for automatically detecting titration end points and correspondingly controlling an automatic cutofi device provided in the ice syringe unit for immediately terminating further delivery of reagent. The titration unit 11 preferably is of the type shown and described in copending application, Serial No. 748,234, filed July 14, 1958, in the names of Conrad M. Jankowski, Manning S. Reynolds, and James M. Thoburn. The disclosure of this application, to the extent it is not inconsistent herewith, is specifically incorporated by reference.

The motor-driven syringe unit includes a syringe barrel 12, of glass or other suitable material, that receives and stores a liquid reagent for measured volumetric delivery thereof to a sample cell 13 of the titration unit. As illustrated, the syringe barrel 12 is preferably arranged vertically and at its upper end includes a discharge nipple 12N in the form of an elongated tubular stem that is adapted for leak-tight connection to one end of a liquidreagent delivery tube 14, the other end of which feeds directly into the sample cell. The delivery tube, as indicated in dotted lines in Fig. l, is adapted for connection to a storage container C for the liquid reagent to draw reagent into the syringe barrel 12 for subsequent measured delivery to the sample cell.

In accordance with this invention, volumetric delivery of reagent from the syringe is registered on a counter 15 that is conveniently visible through the top panel 16T of the main housing 16 of the unit to provide a digital presentation representative of the volume of liquid delivered from the syringe. -The overall arrangement of operating parts of "th motor-driven syringe unit is best shown in Figs. 2 and 3 wherein the syringe is shown as including a conventional piston 17 that is vertically reciprocable through the open bottom end of the barrel 12, with the piston and barrel being mounted in accurate, coaxial alignment at the upper end of an upstanding guide and support assembly 18 that projects through a cylindrical tower 19 that extends above the top panel 161 of the main housing for the unit.

The guide and support assembly includes a hollow outer column 20 threaded externally at its upper end 201", a mounting nest 21 for the syringe barrel in threaded engagement with the upper end of the column 20, a mounting block 22 for the syringe piston 17 arranged in accurate, snug-fitting, non-rotatable, slidable relation in the column, and a rotatable drive rod 23 in the form of a precision screw that projects into a clearance bore 2213 opening through the bottom end of the mounting block, with the drive rod being connected in threaded relation to the block so that rotation of the rod drives the block 22 through the column 20.

The mounting block 22 is in the form of a plunger and is axially recessed at its upper and lower ends to form mounting pockets 22U and 22L for the externally shouldered lower end 178 of the piston 17 and for a connection-nut assembly 25. The assembly 25 includes an antibacklash spring 258 reacting between spaced-apart nuts 25A and 25B that have direct threaded engagement with the drive rod 23, with the lower nut 25B being fixed to the lower end of the plunger 22. Therecess at the upper end of the plunger is internally threadetL as indicated at 22T, and receives an externally threaded mounting nut 26 for anchoring the piston in predetermined alignment within the mounting block or plunger 22.

The mounting nest 21 for the syringe barrel is in. the form of a collar that is internally threaded adjacent its opposite ends, with the lower end of the collar being threaded onto the upper end of the column 20 and. with a barrel nut 27 being threaded intolthe upper end of the collar for securing the shouldered lower end 128 of the syringe barrel in fixed position relative to an internal abutment shoulder 21A located intermediately along the length of the collar 21. The bottom face of the abut- '3 meat shoulder is fiat and provides a solid stop that is engageable with the fiat upper end face of the piston nut 26 forpositively limiting over-travel of the piston through the barrel, thereby protecting the fragile syringe parts.

'Ina power-drivensyringe arrangement, accurate alignment is crucial if excessively frequent breakage of the syringe barrel is-to beavoided. Accordingly,-the-plunger 22 is in accurate, snug-fitting, slidable, contacting eng'agement with the interior of the column to establish coaxial alignment; and the arrangement of the nest 2-1 and the mounting nuts '27 and 26 for securing the barrel andpiston'to-the column and plunger maintains the established alignment.

To provide a cushioned and yet firm mount for the fragile glass barrel and piston, mountingrings 28 of a slightlyyieldable material such as polytetrafiuoroethylene, more commonly'known under the trade name Teflon, are provided on opposite sides of the barrel shoulder 128, with a steel wear ring 29 located between the upper Teflon ring and the barrel nut 27. Similarly a disc 30 of Teflon provides a mounting pad for the bottom face of the pistonanda'Tefion mounting ring 31 and steel wearring 32 are disposed between the upper face of the piston shoulder and the piston nut 26. This cushioned mounting arrangement accommodates a limited adjustment of the axial-alignment of the pistonand the barrel toapermit true coaxial alignment of these parts. It will be noted that the syringe-mounting assembly utilizes a conventional syringe construction for which replacement parts are readily available.

-As=mentionedpreviously, the plunger, whichis driven by rotation of the drive-grod '23, is mounted in non- -rotatable,; slid ingrelation withinthe column 20. Preferably, the plunger'is'providedwith oppositely extending radial arms 33 having rollers 34:suitably journalled thereon withthe arms and rollers projecting through lengthwise'extendingslots 208 provided in the side walls of the column. The rollers are arranged for wheeled engagement withthe-lengthwise edges of the slots to minimize frictional resistance to axial movement of the plunger through the column while preventing rotation of the plunger. In addition, the roller 34 on the right-hand arm (see Fig. 2) serves as an actuator for limit switches 35 and 36.that are fi-xed to the column at axially spaced points thereon; for controlling the limits -of movement "of thesyringe piston 17.

The syringe is powered byselectively energizeable, oppositely acting motor units designated generally at ,37 and 38 which,. in the illustrated form of the invention, are connected to the drivingrod 23 through a threepiece gear-train arrangement. 1

The gear-train arrangement (see Figs. .2 and'4) comprises three coplanar, edgewise .aligned spur gears, the.

outer or motor vgears40 and 41 of which are indirect connection with theoutput shafts 37S and 385 'of the motor unitsandthe central, or driven, gear 42 of which meshes with each of the outer gears andis in coaxial driving connection with the driving rod 23.

Each of the motor units may .be of :a type having a self-contained clutch mechanism between the. motor and the associated outputshaft, with theclutch mechanism being engaged only when the motor is energized.

'Intheillustrated arrangement, motor 371is a fill motor and operates ata constant speed o'f 60 rpm. to drive the gear train in a direction to retract the syringe piston 17 at' a convenient preselected speed, while motor 38is a delivery motor, and operates at a constant speedof 8 r-.p :m. to advance the syringe piston at a considerably slower rate, which is desirable for accuracy in the control 'ofith'e delivery operation.

A'common' basestr ucture is provided-for the various pa'rtsof. the motor-drivensyringe unit. The base structnre cornprises ajbase plate 44 anda plurality of support I'egs"45,' Withthe base platehavin'g' a central opening --through-which ashouldered journal sleeve 46-projects,

with the sleeve being fixed to the base plate by one or more fasteners 46F and disposed in snug relation within the bottom of the mounting column 20, with one or. more additional fasteners 46A securing the mounting column to the sleeve. As is indicated, the motor units are supported above the base plate and have the output shafts thereof extended through the base plate for connection to the motor gears.

Intermediate structure that includes the sleeve 46 which anchors the mounting column 20 to 'the base plate 44 and a shouldered thrust collar 23C rigid on the rotatable drive rod 23 holds the column and rod against relative endwise movement.

The above described motor drive for the syringe offers significant cost advantages over comparable arrangements that depend upon ,a single motor that is reversible and has provisions for variable speed. In addition, the present arrangement is admirably suited for use in a commercial instrument where compactness and simplicityare so important.

Some of the important advantages of the 'unit of this invention are its versatility, convenience, and-accuracy; and of these, accuracy is probably of first importance. In its normal use, the syringe will be called upon to deliver various amounts of reagent and will be turned on and off at appropriate times, either manually or automatically, with the mainfunction of-the syringe being to accurately measure and record the amount of reagent delivered.

According to this invention, anelectric impulse type counter 15 is fixed to the underside of the top plate 16T of "the main housing for convenience in-viewing, andit preferably presents a digital representation of the volume of reagent supplied. The electric counteris controlled by a mechanically operated electric electric switch '47 having direct mechanical connection with the driving system for the syringe. In this disclosure, theelect'r ic switch is shown in engagement with the peripheral teeth of the driven spur gear 42 to open and close once for each tooth and count each tooth as it passes during a liquid-delivering rotating motion of this gear. Preferably, though not necessarily, the switch 47 is arranged so as not to respond when the driven gear is rotating in a liquid-filling sense. There is a particular advantage in this arrangement wherein the electric counter-15 is positioned for convenient viewing through the top panel of the housing and is controlled remotelyby the switch 47,-which is in direct engagement with the main part of the driving system. in that the counting function imposes a minimal-frictional drag .upon the driving system for the syringe-whileavoiding errors'due to cumulative backlash in a series of .mechanicalconnections. Counting with thisarrangement has ;proven tobe highly accurate and repeatable in performance.

The operation ofthe motor-driven syringe unit ..will now be described in connection with its .control circuit, which is illustrated diagrammatically, in Fig.5. Assuming the barrel of thesyringe to be-,empty,-a.-control switch .50 onthetoppanel 16 T is.;turned;to its *fill position to energize the fill motor ;37- throughascircuit that includes the normally closedlimitiswitch .35. When the fill motor is energized, its self-contained clutch} mechanism immediately-engages and connects-the motor 37 to its output shaftgS'lSjordriving-the gear train to retract the plunger 22 and syringe piston-17. This action may continue until the roller '34'of the plunger: engages the lower limit switch35' to interrupt "the energizing circuit. for the fill motor.

Theinstrument is then ready for delivery of reagent andswitch 50 is turnedtoflle deliver position to pick upthedelive fmQtm" 38,through:.the normally'tlbed limit switch 36, while simultaneouslyenergizing .the branch ei reuitfor thevcounter;15. 'Ihisphaseof the operation may either be manual or automatic. In the case of automatic delivery, the terminals 51 of a plug-in receptacle receive a connection plug (not shown) from the end point detector unit 11, while in the case of manual control, the terminals 52 of the receptacle will receive a connection plug from a conventional source of A.C. power (not shown). In either case, the selector switch 53 will be appropriately positioned and this phase of the operation of the instrument is similar.

As the delivery motor 38 is energized, its clutch mechanism engages the output shaft 388 to drive the gear train for rotating the driving rod 23 so as to advance the plunger and syringe piston. As the driven spur gear 42 revolves, the counter switch opens and closes once during the passage of each tooth of this gear to register calibrated counts representative of the volume of reagent delivered.

In the case of automatic delivery, the supply of reagent is terminated when the circuit through the terminals 51 to the end point detector unit is interrupted by the apparatus of the end point detector unit. In the case of manual operation, the control switch must be actuated to terminate the supply.

It should be noted that the clutch mechanism immediately disengages to avoid the possibility of the momentum of the motor causing undesired over-travel of the driving system and of the syringe piston itself. Any such overtravel leads to serious inaccuracies. In this connection, it will be apparent that since the tube 14 may deliver liquid to the sample cell 13 at a point considerably beneath the liquid level of the syringe, a syphoning effect tending to cause over-travel of the piston may be developed. In the present arrangement, however, the piston nut 26 provides a releasable solid connection between the piston 17 and the driving system for resisting such syphoning forces.

Normally, the capacity of the syringe accommodates a number of titrations before refilling is required and the operator is given Warning of the necessity for refilling by the normally closed limit switch 36, which opens upon engagement with the arm carried by the plunger. At that time, a warning light 55 on the top panel 161 is energized to inform the operator that the final titration exhausted the supply of reagent and did not reach an end point.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title 35, of the US. Code and that the claims should be construed as broadly as prior art will permit.

1 claim:

1. In liquid-delivery apparatus, the combination with a syringe that includes an open-ended barrel and a piston reciprocably slidable through one end of the barrel to draw liquid into or eject liquid from the barrel, of support and guide means for said syringe and comprising a hollow mounting column, plunger means abutting one end of said piston and in non-rotatable, reciprocably slidable engagement within said column, drive means including a rotatable rod extending axially through said column into screw-threaded, relatively slidable engagement with said plunger means, intermediate structure securing said column and said rod against relative endwise movement, and a collar releasably securing said barrel to said column in endwise alignment therewith.

2. The apparatus of claim 1 wherein said piston has an external end shoulder, said plunger means has a recess at the end thereof adjacent said piston to form a mounting pocket for said shoulder coaxial with said barrel, and clamping means securing said shoulder within said pocket.

3. In liquid-delivery apparatus, the combination with a syringe that includes an open-ended barrel and a piston reciprocably slidable through one end of the barrel to draw liquid into or eject liquid from the barrel, of support and guide means comprising a hollow mounting column having side walls formed with lengthwise slots,

plunger means abutting one end of said piston and in reciprocably slidable, non-rotatable engagement within said column, said plunger means having arms thereon provided with rollers projecting through said slots to provide frictionless, anti-rotation engagement between said plunger means and said column, drive means including a. rota-table rod extending axially through said column into screw-threaded, relatively slidable engagement with said plunger means, intermediate structure securing said column and said rod against relative endwise movement, and a collar releasably securing said barrel to said column in endwise alignment therewith.

4. The arrangement of claim 3 wherein said drive means is an electric motor, and upper and lower limit switches are mounted at spaced points on said column for engagement by one of said arms for automatically shutting oif said motor.

5. In liquid-delivery apparatus, the combination with a syringe that comprises a barrel having an open end provided with an annular external shoulder and a piston reciprocably slidable through the open end of the barrel and formed with an annular external shoulder, of support and guide means for said syringe comprising a hollow mounting column externally threaded at one end thereof, a sleeve-like nest having an internal abutment shoulder intermediately therein and internally threaded at opposite open ends thereof, said nest having one end thereof in threaded engagement with said column, with the shouldered end of said barrel being received in the other end of said nest and a barrel nut securing said barrel in said nest, a plunger in non-rotatable, reciprocably slidable engagement Within said column, said plunger having an internally threaded mounting pocket at the end thereof adjacent the shouldered end of saidpiston, a piston nut securing the shouldered end'of said piston in said pocket in coaxial alignment with said barrel, drive means including a rotatable rod extending axially through said column into screw-threaded, relatively slidable engagement with said plunger, and intermediate structure securing said column and said rod against relative endwise movement.

6. In liquid-delivery apparatus, the combination with a syringe that includes an open-ended barrel and a piston reciprocably slidable through the barrel to draw liquid into or eject liquid from the barrel, of a drive mechanism for reciprocating said piston and comprising a rotatable driven shaft, means connecting said shaft to said piston for moving said piston through said barrel in opposite directions in accordance with the direction of rotation of said shaft, and means for rotating said driven shaft and comprising first and second motor units having output shafts rotatable in opposite directions, motion-transmitting means connecting one of said motor units to said driven shaft for rotating the same in one direction, motion-transmitting means connecting the other of said motor units to said driven shaft for rotating the same in the opposite direction, and means for selectively driving one or the other of said motor units.

7. The arrangement of claim 6 wherein each of said motor units is an electric motor having a self-contained clutch between the motor and said output shaft thereof, with said clutch being automatically engaged and disengaged simultaneously with the energization and deenergization, respectively, of the motor.

8. The arrangement of claim 6 wherein the motor unit which controls forward or liquid-ejecting movement of the piston is a relatively slow-speed device and the other motor unit is a relatively fast-speed device.

9. The arrangement of claim 6 wherein the motiontransmitting means for connecting the motor units to the driven shaft comprises three coplanar, successively intermeshing spur gears, with said two output shafts and said driven shaft being fixed to separate ones of said gears.

10. The arrangement of claim 9 wherein an electric switch is mechanically connected to the spur gear that is asserts fixe to :seid ridriven :shaft :to ppen and close once for each-predetermined increment ;of rotation thereof in the pistomadvaneing direction-and is connected in series with an electric-impulse counter;for actuating the same.

-l;1. An instrument for the volumetric delivery of liquid and comprisinga housing, supporting structure within said housing and including a ,base plate and depending support legs therefor, a hollowcolumntfixed to said plate with the axis of said columnextending generally normal to the plane of said plate, aplunger in non-rotatable, reciprocably slidable engagement'within said column,,a rotatable-driven-rod journalled in said base plate and extending axially through said column 'intoscrew-threaded, driving engagement with said plunger, a-pair of unidirectional motor units supported on said base plate in flanking relation to said column and having output, shafts projecting downwardly throughsaid base plate, said output shafts being rotatable in opposite directions, a separate spur gear-fixed to each. of said output-shafts and to said driven shaft, with said spur gears beingarranged beneath said base plate in coplanar, successive, intermeshing engagement, and means for selectively driving ,one ,or the other of said motor units.

12. In liquid-deliverytapparatus, the combination with a syringe thatincludes an open-ended barrel and a'piston reciprocably slidable-through the barrel to draw liquid into or eject liquid fromthe barrel, of a drive mechanism forreciprocating said piston and comprising a rotatable driven shaft, means connecting said shaft ,to said piston for moving said piston throughsaid barrel in opposite directionsin accordance with the direction'of rotation of.-said shaft, selectively operable motor meansfor rotating, said driven'shaftin one direction or the other motion-transmitting means for-connectingthe motor :means to the driven shaft and including a spur gear'fixed to said driven shaft, an electric impulse counter, and an electric switch mechanically connected to the spur gear-toopenand close once for each predeterminedincrement ofrotation thereof and connected in series :with said counter for-actuating the same.

13. In liquid-delivery apparatus, the combination with a syringe that includes an open-ended barrel and a piston reciprocably slidable through one end of the barrel to draw liquid into or eject liquid from the barrel, of support and guide means for said syringeand comprising a hollow mounting column, plunger means abutting one end ofsaid piston and in non-rotatable, reciprocably-slidable engagement withinsaid column, drive means including 1. rotatable rod extending axially through said column, one end of-saidrod in screw-threaded, relatively slidable engagement with said plunger means, and the otherend connected to a gear train, said gear train includinga spur gear fixed to said rod, a driving motor having an output shaft in direct connection withthetgear train, an electric impulse counter, and an electricswitch'mechanically connected to the spur gear to open and close once for each predetermined increment of rotation thereof in its piston-advancing direction and connected in series with said counter for actuating the same. 7

14. An apparatus for the syringe delivery of liquid comprising a syringe having a piston in an open-ended barrel, a syphon-creatmg supply tube communicating with said open-ended barrel for delivering liquid therethrough in response to movement therethrough of the liquidejecting piston, driving mechanism comprising a plunger for driving engagement with said piston, motor means for driving said plunger in the direction of movement of the piston, means for cutting off said motor means and manual-ly releasable means for locking said plunger to said piston to anchorthe piston to the driving mechanism'to enable the driving mechanism to resist syphoning forces tending to cause over-travel of the piston following cutoff of the motor means.

15. ,In liquid-delivery apparatus, the combination with a syringe that includes an openfended barrel and a piston reciprocably slid-able through the barrel to draw liquid into or eject liquid from the barrel, of a drive mechanism for reciprocating said piston and comprising a rotatable driven shaft, means connectingsaid shaft to said piston for moving said piston through said barrel :in opposite directions in accordance with the direction of rotation. of said shaft, selectively operable motor means for rotating said-driven shaft in one direction or the other, motiontransmitting means for connecting the motor means to thedriven shaft, an electric impulse counter, and anelectric switch mechanically connected to said drive mechanism to open and close once in responseto each predetermined increment of rotation of said driven shaft and electrically connected to control actuation of said counter.

References Cited in the file of this patent UNITED STATES PATENTS 

